The present invention relates to a self-cleaning filtering apparatus for filtering a product to be filtered, comprising a body, an inner filtering basket communicating with an inlet duct for the product to be filtered and a drain for discharging waste and forming, with the body, a peripheral space communicating with an outlet duct for the filtrate, scrapers being adapted to be rotated inside the basket to clean it.
The applications of such an apparatus are numerous, not to say universal, and it is met with in most transformation industries where it is necessary for example to filter solvents, adhesives, glues, polymers, emulsions, sludges, resins, paints, varnishes, grains, tars, pigments, detergents, food products, etc..
It is also met with in the paper-making industry and particularly as a coating sauce which is a liquid of medium viscosity (1000 to 2000 cp). It was by considering this particular application that the Applicant raised the problem which is at the basis of the invention of the present application. This application will therefore be described in greater detail. However, the Applicant does not intend limiting the scope of his application for all that, the description of this particular application being given for purely pedagogic reasons. The invention applies to products of any viscosity.
Crude paper does not make perfect printing by inking possible, because of the uneven and absorbent nature of its surface. It is then necessary to eliminate the unevennesses, to stop up the pores and give the paper an appropriate appearance For this, the crude paper is coated with a coating sauce, which is a liquid of medium viscosity, in a station of the paper-making machine situated between the rollers for drying the crude paper and the station for drying the coated paper.
Before being introduced into the conditioner, the coating sauce is first of all stirred in vats and filtered through a vibrating strainer, so that it is considerably mixed with air; the impurities of the air are often more prejudicial than the solid impurities.
An object of the invention is then to eliminate the air bubbles from the product to be filtered as much as possible.